The present invention relates to an image pickup apparatus, particularly to an image pickup apparatus in which a lens hood is mounted on the front side of an optical system.
When a point light source is put in an object at the time of shooting by a video camera, non-imaging light reflected by an air-glass joint plane of a shooting lens or the like reaches the image pickup screen to form irregular light spots, leading to the generation of flare and to a trouble in image pickup.
Therefore, it has been an ordinary practice to mount a lens hood on the front side of the shooting lens of a video camera so as to prevent the generation of flare at the time of shooting. However, where the peripheral surface of the lens hood is long to the front side, an image pickup screen with its corner portions lost is obtained; in view of this, a short lens hood has been used.
When a short lens hood is thus mounted on the front side of the shooting lens at the time of shooting by a video camera, an image pickup screen with its corner portions not lost can be obtained, but the amount of light received by the shooting lens is so large that a point light source is easily put in to the object side, leading to the generation of flare on the image pickup screen.
In view of the above, as is disclosed, for example, in Japanese Patent Laid-open No. Hei 9-18757, a system has been proposed in which a lens hood and a dowser are provided on the front side of a shooting lens in a video camera, the incident light is contracted by the dowser, and the amount of light coming from the point light source on the object side is reduced, thereby preventing the generation of flare on the image pickup screen.
On the other hand, in some cases, a conversion lens is mounted for widening the angle of view in shooting. The conversion lens is an auxiliary optical system which is mounted on the front side of the shooting lens, and, where such an auxiliary optical system is used, it is necessary to detach the lens hood and to mount the conversion lens in the lens food mounting position. Therefore, the flare preventive function by contracting the incident light with the dowser of the lens hood cannot be expected, and the operation of detaching the lens hood is laborious.
Japanese Patent No. 2500892 discloses an auxiliary optical system mounting adapter for mounting an auxiliary optical system to a camera including a hood frame body having an opening portion corresponding to the angle of field of a shooting lens. The hood frame body is provided on the front side of the shooting lens as one body with a camera main body. The adapter includes a mount portion to which the auxiliary optical system can be detachably mounted, a positioning frame disengageably fitted in the opening portion of the hood frame body, a fixed claw capable of being disengageably engaged on one side of the peripheral edge of the opening portion, and a movable claw which can be disengageably engaged on the other side with respect to the center of the opening portion and which is displaced in the engaging-disengaging direction by being pushed by a lens-barrel of the auxiliary optical system when the auxiliary optical system is mounted.
The use of such an adapter makes it possible to mount an auxiliary optical system such as a conversion lens on the front side of the food frame body, and eliminates the need to detach the hood frame body. However, where the auxiliary optical system such as a conversion lens is used, the incident light is refracted by the conversion lens so largely that the incident light contracting effect of the hood frame body cannot be expected. Namely, the incident light contracting effect of the dowser of the lens hood cannot be displayed.